In many instances it is necessary or desirable to form or mold tacky materials by hand, generally using protective gloves. For example, tacky resinous materials may be molded by hand into certain forms or shapes. The resinous material may have a resinous matrix, whether filled with other materials or not, or may be a resin impregnated into a porous substrate. Practical uses of such materials include knitted or woven fiberglass impregnated with a tacky material that may be used to repair water pipes or boats, tacky epoxy materials that may be used in repairing mufflers and automobile bodies, tacky epoxy resin wraps that may be used to repair poles such as utility poles like telephone poles, and the tacky, curable materials that are widely used in making orthopedic casts and splints. In each of these cases a lubricant may be applied to protective gloves to prevent the gloves from sticking to the tacky resinous material.
In forming orthopedic casts and splints, in particular, it has become necessary to devise a simple and versatile means of lubricant delivery to a glove. Casts and splints are widely used for immobilizing a body member, for example to allow a broken bone to heal properly. Plaster of paris casts have recently been largely replaced in many applications by orthopedic bandages or sheets impregnated with tacky synthetic resin mixtures. The synthetic resins used in combination with certain knitted or woven substrates offer a number of advantages over the old plaster of paris materials. Casts made from the synthetic materials are lighter, stronger, harden more quickly, allow for better air circulation, and are not water sensitive.
Among the synthetic resin compositions used to prepare casting materials are water-activated or water-curable synthetic resin compositions and thermoplastic resin compositions. Like the old plaster casting material, the water-activated or water-curable synthetic resin impregnated bandages or sheets, which may also be called tapes, are wetted before application to the body member. The water begins the curing reaction that hardens the cast. Other compositions for casting materials use synthetic resin compositions employing different kinds of curing mechanisms, for example crosslinking through unsaturation.
The synthetic resin orthopedic sheets being used, however, are more difficult to mold about the body member than the old plaster of paris casting sheets due to the tackiness of the resin. This problem may be overcome by interjecting a lubricant between the tacky bandage and the surface, usually a gloved hand, that is being used to mold the cast.
Various means of delivering the lubricant to the glove have been suggested. A mixture of water, sorbitol, mineral oil, and silicone fluid is commercially available from 3M Co., St. Paul, Minn., under the tradename Cast Cream for application to the gloves after wrapping the cast but before molding the cast. Richard et al. disclose a lubricated glove for applying orthopedic cast bandage in EP 712 618. A hydrophilic lubricant is added to a flexible elastic glove material. In U.S. Pat. No. 5,438,709, Green et al. disclose lubricated gloved formed from a elastomer, preferably a latex, with a lubricating polyvinyl alcohol external coating. The PVA may be thickened with, e.g., rhamsan gum. The external coating may be applied by dipping the glove in a solution of the lubricant, followed by drying the coating. In U.S. Pat. No. 5,439,439, Green et al. disclose a similar lubricated glove coated with polyvinylpyrrolidone. These gloves are believed to be difficult to manufacture reproducibly. A further drawback to these coated gloves is that the person molding the cast has no control over the amount of lubricant applied to the gloves.
Another approach that has been used is to "prelubricate" the casting sheet or tape, i.e., to provide a lubricant to a part of the casting sheet that is impregnated with the tacky resin, as opposed to the current method of applying the lubricant to the gloves. Scholz et al. disclose in U.S. Pat. Nos. 4,667,661 and 4,774,937 curable resin-coated sheets prelubricated with a hydrophilic lubricant. The lubricant is present in an amount sufficient to reduce the kinetic coefficient of friction of the sheet surface to less than 1.2. Dull et al., U.S. Pat. No. 4,937,146, impregnate a tape with a mixture of a resin and a non-polar hydrophobic lubricant. The mixture is unstable to the extent that at least part of the lubricant migrates to the surface of the coated sheet to impart low surface tack. Prelubricating all surfaces of the sheets, however, has the drawback that more lubricant is used than is necessary or desirable, and there is no control over the amount or time of application. For instance, it may be desirable to have the wrapped layer stick to one another without slipping and to have the end of the sheet or bandage stick to the surface of the casting sheet wrap in order to terminate the application of the sheet. Moreover, incorporating certain lubricants, such as mineral oil, into the curable resin composition may result in longer set time due to the dilution of the resin curing sites. It is also necessary to avoid a lubricant that would react with the casting resin during storage, as reaction could harden the resin and make the product unusable.
A water-soluble liner layer for casting sheets is disclosed by Scholz et al., WO 94/23769. The liner prevents pooling of resin from out of the casting sheet roll and prevents adhesion of adjacent layers of the roll. The reference discloses that the liner dissolves when the casting sheet is immersed in water to expose the casting sheet. The dissolved liner may also lubricate the casting sheet. This method of lubricating the whole length of the casting sheet, however, is subject to the same shortcomings as the pre-lubricating method.
The present invention provides an improved means of delivering a desired amount of lubricant to selected sites on the gloves one or more times when working with tacky materials, in particular tacky resins and polymers, and to articles used in such methods. In one embodiment, the present invention concerns delivering lubricant to gloves during forming an orthopedic cast to prevent the gloves from sticking to the casting material, as well as an orthopedic casting kit for carrying out the method. A lubricant-impregnated porous substrate and a package containing one or more such substrates is also provided.
In one method of the present invention, a porous substrate is impregnated with a lubricant. The impregnated substrate is then used to deliver lubricant to the gloves of the person forming the tacky resin or cast material to prevent the gloves from sticking to the resin material or cast tape during application and molding of the material. The present method offers a number of advantages over prior methods. First, only as much lubricant as is necessary is applied to the gloves and the cast being molded. Accordingly, a certain amount of tackiness may be maintained if desirable. Secondly, because the lubricant is not admixed with the curable composition, or applied to the cast sheet or tape for the purpose of significantly affecting its tackiness, the lubricant may be selected from a wide variety of materials, including materials that might be reactive toward the curable composition of the casting sheet or other tacky material being formed, or that would otherwise affect shelf life or performance. In addition, the lubricant may be reapplied to the gloves as desired during application and molding of the cast material, or while working with other tacky materials. Thus, the level of tackiness can be controlled according to the preference of the individual casting technician. Finally, the lubricant need not be hydrophilic, as is required in many of the prior methods described above.